Yes, I know that trolling is the norm on this message board but we should not lower our standards.
For an e-reader to fail to provide syncing of annotations is an embarrassment in 2022. It was true 10 years ago, and even more so today.
E-books are very nice to read in Marvin (still nicest out of all iOS e-readers, I think), but Marvin is and always was an unfinished product. Let's not fool ourselves.
It appears that Marvin is forever abandonware now, so perhaps trying to get MapleRead to support and do everything that Marvin does, and then beyond, is the most realistic way to go forward from here.